There are various methods for determining when the regenerative control is performed. For example, there is a method for automatically functioning it according to an acceleration (e.g. Patent document 1).
According to this method, the regeneration automatically begins without any user's operation. Therefore, it is expected that an amount of regeneration increases by performing the regeneration even in a running state where the regeneration has not been performed. On the other hand, if the regeneration automatically begins when the user does not intend the deceleration, the user may feel uncomfortable.
Moreover, another document (e.g. Patent document 2) discloses a motor driving control apparatus that includes (a) a detector to detect a start instruction or stop instruction of regenerative control by a driver; (b) a control coefficient calculation unit, upon detecting the start instruction of the regenerative control by the detector, to specify a first vehicle speed at a detection timing and set a predetermined value for a control coefficient for a target amount of regeneration, and to increase a value of the control coefficient when a current vehicle speed is faster than the first vehicle speed, and decrease the value of the control coefficient when the current vehicle speed is slower than the first vehicle speed; and (c) a controller to control driving of the motor by the value of the control coefficient from the control coefficient calculation unit and the target amount of regeneration. According to this document, the start instruction of the regenerative control is detected by an inverse pedal rotation whose angel is equal to or greater than a predetermined phase angle, ON of an instruction switch for the start instruction of the regenerative control or a series of ONs of a brake switch within a predetermined time period.
According to the technique described in this document, it is possible to function a regenerative braking force while taking into consideration the driver's intention and perform the regenerative control so as to keep the first vehicle speed as much as possible. However, it is assumed that the driver remembers an operation to perform the start instruction of the regenerative control with intention to designate the first vehicle speed. Moreover, according to the aforementioned technique, the vehicle speed at the start instruction of the regenerative control is tried to be kept. However, the vehicle speed preferable for the driver may not always be the vehicle speed at the start instruction of the regenerative control.
Patent Document 1: Japanese Patent No. 5655989.
Patent Document 2: Japanese Laid-open Patent Document No. 2014-90539
Namely, there is no technique for performing the regenerative control according to a running state presumed as user's intention that appears in the braking operation.